Use of ¹⁵N NMR spectroscopy to probe covalency in a thorium nitride

Abstract

The first isolable molecular thorium nitride, [(NR2)3Th(μ-N)Th(NR2)3]−, was synthesized by reaction of [Th{N(R)(SiMe2)CH2}(NR2)2] with NaNH2 and characterized by X-ray crystallography, 15N NMR spectroscopy, and DFT calculations.

Synthesis and electronic structure analysis of the actinide allenylidenes, [{(NR2)3}An(CCCPh2)]− (An = U, Th; R = SiMe3)

“…The situation is reminiscent of the SOC effects on the shielding of nitrogen atoms bound to Th that we identified recently. 60,61 The calculated 13 C chemical shifts for complex 4 (Tables S3 and S7) also agree reasonably well with the experimental data. For example, the calculated Cα shift for complex 4 is 211 ppm (expt.…”

Thorium-nitrogen multiple bonds provide evidence for pushing-from-below for early actinides

“…Unfortunately, reductions with these metals are more difficult to control, and intractable product mixtures were obtained. However, using the new thorium-parent-amide [Th(Tren TIPS )(NH 2 )] ( 5 ) – which is only the third example of a structurally authenticated Th–NH 2 bond 40,72 , prepared here by reaction of NH 3 with the known cyclometallate [Th{N(CH 2 CH 2 NSiPr i 3 ) 2 (CH 2 CH 2 SiPr i 2 CHMeCH 2 )}] 79 (see Supplementary Figs. 7–9) – we find that 5 can be deprotonated with strong bases; treating 5 with Bu t Li or NaCH 2 Ph in benzene affords [{Th(Tren TIPS )(μ-NHM)} 2 ] (M = Li, 4Li ; Na, 4Na ) in 56 and 38% isolated yields, respectively, Fig.…”

“…In contrast, molecular uranium-nitrides 43 were first prepared under matrix isolation conditions 42,44–49 , then a range of bridging nitrides were isolated and characterised 50–65 , or inferred from the products of transient species 66 , and then terminal U≡N triply bonded species were finally secured 67–71 . During publication of this work a bridging thorium-nitride was reported 72 , but isolation of a terminal molecular Th≡N triple bond under normal experimental conditions remains an unmet challenge.…”

Exceptional uranium(VI)-nitride triple bond covalency from 15N nuclear magnetic resonance spectroscopy and quantum chemical analysis

“…The generally accepted chemical bonding picture is that for early actinides the bonding varies from ionic to polarised-covalent as a function of An-oxidation state and ligands, with this range sitting intermediate to the ionic lanthanides and usually much more covalent d transition metal complexes 5,7,8,10,11 . Probing actinide covalency is challenging, but in recent years progress has been made using experimental approaches, underpinned by quantum chemical calculations, including K-edge X-ray absorption near edge spectroscopy [12][13][14][15][16][17][18] , pulsed electron paramagnetic resonance spectroscopy 19 , and nuclear magnetic resonance (NMR) spectroscopy [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] . These investigations have begun to place the bonding descriptions of An-L bonding on a rigorous, quantitative footing, and have been consistent with the status quo bonding description of early actinides.…”